1. Field of the Invention
The present invention relates generally to apparatus for applying control forces to magnetically suspended members and torques about the suspension axes of magnetically suspended members. It will be understood that, in its broad aspects, the invention is useful in applying forces or torques to any magnetically suspended member such as, for example, in a precision pointing system wherein the pointed element, such as a space telescope, is supported in a platform, coarsely supported and positioned by electromechanical actuators and finely supported and positioned by a magnetic suspension. Also, the invention finds use in magnetically suspended, high speed scanners wherein it is desired to apply small angular or lineal forces or angular torques for fine focusing or scanning purposes.
2. Description of the Prior Art
All magnetic suspensions include some form of magnetically permeable gaps between the fixed member and the suspended member and the generation of strong magnetic fields across these gaps to provide the suspending forces. The configurations of the gap-forming structures may take many forms. The magnetic fields may be produced by wholly active means, that is, generated by electromagnetic fields only, or they may be a combination of permanent magnet fields (passive fields) and electromagnetic fields (active fields). Typical structures utilizing the latter types of magnetic suspensions are disclosed in the A. V. Sabnis U.S. Pat. No. 3,976,336 for a "Magnetic Suspension Apparatus," issued Aug. 24, 1976 and in the J. R. Dohogne, A. V. Sabnis U.S. Pat. No. 4,090,745 for a "Magnetic Suspension Apparatus with Magnetic Stiffness Augmentation," issued May 23, 1978, both assigned to Sperry Corporation. Both of the latter patents and the Studer U.S. Pat. No. 4,000,925 disclose magnetic suspensions for suspending gyroscopic rotors.
Another form of a magnetically suspended gyroscopic device is the magnetically suspended, free-rotor torque feed back gyroscopic rate sensor of the above referenced copending J. R. Dohogne application. This device is typical of force or torque feed back rate sensors wherein the rotor is maintained in a substantially zero deflected position relative to its supporting housing by feeding back currents to torque motors which apply torques on the rotor to oppose any rotor tilt, such currents being proportional to the tilt-causing force, for example, the angular rate of the vehicle on which the sensor is mounted. The present invention is particularly applicable to such sensors and will be described in connection therewith.
Typical prior art torquing or positioning of magnetically suspended members involved, for example, increasing and decreasing the primary magnetic suspension fields in solenoid fashion. This is particularly applicable to the all-active types of magnetic suspensions. In other cases, the application of torques or forces on the magnetically suspended member which includes active and passive types of suspensions, involved exerting such torques or forces on elements of the member completely independently of the magnetic suspension field itself. Such schemes require the direct modulation of the primary source of the magnetic suspension field; i.e., the variation of the current supplied to the coils of the field generators or completely separate and integral torque motors or force generators acting independently of the magnetic suspension, resulting in design complexity and increased weight and cost.